Time-delay switch



March 23, 1948. R, D, RANDALL 2,438,186

TIME DELAY SWITCH Filed Jan. 25, 1946 llltlllll:

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Patented Mu. 23, 194s TIME -DELAY SWITCH Ross D. Randall, Chicago, Ill., assigner to Stewart-Warner Corporation, Chicago, lll., a oorporation of Virginia Application January 25, 11946. Serial No. 643,329

6 Claims. 1

The present invention relates to time delay switches and, more particularly, to a time delay switch which acts to open an electric circuit and to lock the circuit in the open position whenever an electric current is caused to flow through the switch for an excessive length of time. Such switches are useful in many applications. Speciilc uses need not be given, however, since the present invention resides in the switch itself rather than in a particular circuit using such a switch.

It is an object oi the present invention to provide an improved lock-open type safety switch having time delay characteristics which can be manufactured at exceptionally low cost.

A further object of the present invention is to provide a novel switch having these characteristics and in which the switch parts need not be kept to close tolerances.

Yet anotherl object of the present invention is to provide a novel time delay' switch of the manually reset type which is sure in operation and which has long life and trouble-free characteristics.

Other objects and advantages will become apparent from the following description of a preferred embodiment of my invention, which is illustrated in the accompanying drawings.

In the drawings, in which similar characters of reference refer to similar parts throughout the several views:

Fig. 1 is a side view of a time delay switch embodying the present invention;

Fig. 2 is an end view of the switch illustrated in Fig. l: while Fig. 3 is a view of the switch shown in Figs. l and 2 as viewed from below.

The elements forming the switch of the present invention are mounted upon -a base I0 which may comprise a rectangular sheet of insulating material, to which a U-shaped metal bracket i2 is secured by screws I3. The bracket is out and bent from sheet metal and is so arranged that the two arms of the U project upwardly normal to the plane of the base, these two arms being drilled to permit the passage therethrough of a resetting plunger I4. This plunger comprises a piece of metal rod having a button EG of any suit.- ab'le material, secured to its outer end. Movement of the rod Hl can take place in a longitudinal or rotational direction only and is limited in its lengthwise movement by C-washers I8 and 20 which are snapped into annular grooves formed in the rod I4. These washers are longitudinally so spaced that when the rod is in its outward pon 2 sition with the washer 2li against the inner face of the outer arm o! the bracket I2, the end 22 opposite the button i6 projects through the adiacent arm a matter of a quarter of an inch or so. When the button is pushed inwardly, the plunger moves about one quarter inch before the washer I8 is brought against the face of the bracket arm. Between the arms of the U-shaped bracket i2, the rod I4 is surrounded by a coil compression spring 2l, one end of which bears against the arm of the bracket adjacent the end 22 while the opposite end of the spring bears against the face of the C-washer 20. The spring, therefore, urges the knob IB and plunger Il outwardly and will return these elements to this position after they have been manually pushed inwardly.

One of the electric contacts 26 oi the device is mounted upon a bracket 28 which is fastened by means of screws 36 to the base i0. This contact 26 is arranged considerably to one side of the plunger I4 and has its axis in general parallel to the axis of the plunger. This contact 26 co-opcrates with a contact 32 mounted at the end of a lever 34 which rocks about an annularly lgrooved pin 3B. This pin is located in a position approximately midway between the end 22 of the rod M and the contact 26. A slot $8 in the side of the bar adjacent the bracket i2 fits into the annular groove in the pin, so that although the bar can rock around the pin, it cannot move vertically relative thereto because of the engagement of the edges of the slot with the sides of the groove.

The bar is normally rotated around the pin 36 into such a position that the contact 32 is separated from the contact 26 by means of a coiled tension spring 40, one end of which hooks through a hole formed in a wing l2 of the U-shaped bracket l2, the opposite end of the spring being passed through a hole N near the inner edge oi the bar 3l in a position closely adjacent to the slot 33, but on the side of the slot opposite the end which carries the contact 32. Although the spring tu tends to swing the bar 34 around thepin 38 so as to separate the contact 32 from the contact v36, this rotational movement is inhibited when the edge of the bar 34 at a point below the point of attachment of the spring 40 comes into contact with the end 22 of the rod i4.

At its lower end, the bar 34 is provided with an arcuate edge 46 ending at a notch $8 at the side of the bar toward the bracket l2. This edge fits within a slot Q9 in the upwardly bent end 50 of a bimetal blade 52, the opposite end of which is secured by means of screws -64 to a forwardly bent wing-like extension 56 formed as 3- a portion of the bracket I2. The bimetal' blade 52, when cool, assumes the position shown in full lines in Fig. 1 in which the slot 49 embraces the end of the bar 46. and with the edge oi' the notch 48 pressing against the end of the bimetal blade.` In this position, the spring 40 urges the contact 42 against the contact 26 while the end of the slot 38 is lifted'slightly away from the pin 36,

The bimetal blade 52 4is provided with an electric heating element 58, one end of which is connected to a bracket 60 having a terminal screw 59, thereon, while the opposite end is grounded to the yblade 52 adjacent the upturned end 50. The circuit is completed by way of the blade 52, the bracket wing 66, and to a terminal post 6I thereon, and by way of a pigtail lead 62 to a point 64 on the bar 34, this point being adjacent the slot 38. From the ba'r 34, the circuit continues through the contact 32 to a terminal 66 on the bracket 28.

The device operates in the following manner. When the .button I6 is pushed inwardly, the plunger end 22 urges the lower end of the bar outwardly until the contact 32 is 'brought against the contact 26, the bai` rocking around the pin 36 and against the tension of the spring 40. After the contact 32 has been brought against the contact'26, the upper end of the bar 34 can no longer move and therefore the end of the slot 38 is lifted away from the pin 36 upon slight further pivotal movement, the pivoting point shifting from the pin 36 to the contacts 32 and 26. After the end of the slot 38 has been moved away from the pin 36 a slight amount, the end 50 of the thermostatic blade snaps into the notch 48 and immediately thereafter the 0washer I8 is brought against the face of the bracket I2, thereby stopping infward movement oi the button I6 and plunger I4.

The button I6 is then released and it and the plunger I 4 are returned to their original positions by the spring 2-4, with the -c-'washer 20 against the inner face of the end of the bracket I2. During return movement of theplunger I4, however, the lower end of the bar 34 does not follow the plunger end 22, since the bar is retained by the end 50 of the thermostatic blade 52 resting in the notch 48. The device is, therefore, in the set position.

In the set position, the arm 34 rests Iwith the `contacts 32 and 36 together, while at the opposite end, the notch 48 engages the end 5,0 of the thermostatic blade. It is held in this position by the spring 40 and the end of the slot 38 is free of engagement of the pin 36. The bar is prevented from twisting about its longitudinal axis, since it is held within the slot in the pin 36 andthe slot 49 in the blade 52.

Whenever the switch is energized, the heating element 58 begins to raise the temperature of the bimetal blade 52 and if this condition continues for an abnormal length of time, the bimetal blade reaches such a temperature that it bends downwardly to the broken line position, so as to cause the end 50 of the blade 52 to move out of engagement with the notch 48. As the spring 40 rotates the bar around the pivot point comprised of the contacts 32 and 36, the end 38 of the slot lis soon brought into engagement with the pin 36, and as the bar continues to move in the same direction, the contacts 32 and 36 are quickly separated and the bar 34 comes to rest with its edge against the end 227er the plunger I4. Subsequent cooling of the bimetal blade 52 causes the end 50 to be urged upwardly, so that soon after the circuit has been interrupted it can be reclosed by pushing inwardly upon the button I6.

Having described my invention, what I claim as new and useful and desire to secure by Letters Patent ofthe United States is;

1. A time delay switch of .the type including a bimetallic element and a heating element arranged in thermal relation therewith, comprising, in combination, a stationary contact, a movable contact associated therewith, a pivotally mounted blade carrying said movable contact at one end, a'latching mechanism, including said bimetallic element, associated with the opposite end of said blade adapted to unlatch said blade when heated, a pivot pin associated with said blade at a point between said stationary contact and said latching mechanism, said pin having a groove therein, said blade having a slot therein adapted to i'lt said groove, resilient means connected to said blade adapted to rotate said blade around said pivot pin so as to separate said contacts -when said blade is unlatched, and manual means adapted when actuated to urge said blade in the opposite direction so as to rotate said blade around said pin to bring said contacts together and thereafter to urge said fblade slightly away from said pin and into latching position, said slot in said blade and said groove in said pin cooperating to prevent the tilting of said blade about its transverse axis or rotation of said blade about its longitudinal axis.

2. A time delay switch of the type including a bimetallic element and a heating element arrangedin thermal relation therewith comprising, in combination, a stationaryA contact, a movable contact associated therewith, a pivotally mounted blade carrying said movable contact at one end thereof, a latching mechanism, including said bimetallic element, associated with the opposite end of said blade adapted to unlatch said blade when heated, a pivot pin associated with said blade at a point between said stationary contact and said latching mechanism, said pin having a groove therein, said blade having a slot therein adapted to it said groove, resilient means connected to said blade adapted to rotate said blade around said pivot pin so as to separate said contacts when said blade is unlatched, and manual means comprising a freely iloating plunger adapted when actuated to urge said blade in the opposite direction so as to rotate said blade around said pin to bring said contacts together and thereafter to urge said blade slightly away from said pin and into latching position. said slot in said blade and said groove in said pin cooperating to prevent the tilting of said blade about its transverse axis or rotation of said blade about' its longitudinal axis.

3. A time delay switch of the type including a bimetallic element and a heating element arranged in thermal relation therewith comprising. in combination, a blade having a notch formed in one edge thereof between its ends, a movable contact mounted on one end of said blade, a stationary contact adapted to cooperate with said movable contact, a latching mechanism including said bimetallic element associated with the opposite end of said blade adapted to unlatch when heated, a large diameter pin having a deep annular groove formed therein adapted to receive said notch, forming a pivot for said blade, the walls of said groove engaging the sides of said notch to prevent rotation of said blade about its longitudinal or transverse axis, resilient means urging said blade into open contact position. and manual means comprising a freely oating plunger ior resetting said switch.

4. A time delay switch of the type including a bimetallic element and a heating element arranged in thermal relation therewith comprising, in combination, a blade having a notch formed in one edge thereof between its ends, a movable contact mounted on one end of said blade, a stationary contact adapted to cooperate with said movable contact, a latching mechanism, including said bimetallic element, associated with the opposite end ci said blade adapted. to unlatch when heated,4 a large diameter pivot pin having an annular groove formed therein adapted to receive said notch, resilient means urging said blade into open contact position, and manual means for urging said switch into closed position, said means operating to rotate said blade about said nin until said contacts are closed, then rotating said blade about said contacts to latchn ing position to lift said blade ofi said pivot, the walls of said .groove engaging the sides ot said notch in all positions ol? said blade to 'prevent rotation or said blade about its longitudinal or transverse axis.

5. a time delay switch of the type including a binietallic element and a heating element anranged in thermal relation therewith comprising, in combination, a stationary contact, a movable contact associated therewith, a pivotaliy mounted blade having a nrst end and a second end carry ing said movable contact at said rst end, a latch= ing mechanism including said bimetailic element associated with said second end of said blade adapted to unlatch said blade when heated, means -forming a notch in said blmetallic element adapted slidably to embrace the sides of said second end of said blade, a pivot pin associated with said blade at a point between said stationary' contact and said latching mechanism, said pin having a groove therein, said blade hav ing a. slot therein adapted to t said groove,`re silient means connected to said blade adapted to rotate said blade around said pivot pin so as to separate said contacts when said blade is un- Sli tuated to urge said blade in the opposite direction so as to rotate said blade around said p to bring said contacts together and the?v to urge said blade slightly away from s and into latching position, said slot in said bin. cooperating with said groove in said pin and said notch in said birnetallic element cooperating with said second end of said blade to prevent the tilting of said blade about its transverse axis or rotation of said blade about its longitudinal axis.

6. A time delay switch of 'the type including a bimetallic element and a heating element arA ranged in thermal relation therewith, comprising, in combination, a blade with a first end and a second end having a notch formed in one edge thereof between said ends, a movable contact mounted on said first end of said blade, a stationaiy contact adapted to cooperate with said movable contact, a latchngmechanism includ-a ing said bimetallic element associated with said second end of said blade adapted to unlatch when heated, means forming a notch in said bimetallic element adapted slidably to embrace the sides of `said second end of said blade, a large diameter ROSS ll REFERENCES tJITElll The following references are oi record in the 4@ ille of this patent:

latched. and manual means adapted when ac- UNITED STATES PATENTS Number l Name Date 1,914,529 Rich June 20, 1933 2,114,512 Weschcke Apr. 19, 1938 2,416,266 Landmeier Feb. 18, 1947 

